I did this about a week ago, but it still needs some work that I can't seem to focus enough to give it. If anyone has a few minutes and a detail oriented eye, please go through and look for weird wording/capitalization/consistency issues. Very much appreciated.
Can I edit/delete an entry in a community journal?
If you posted the entry yourself, you can both edit and delete it, as long as you are still a member of the community. If you are the community's maintainer, you can delete the entry, but you can't edit it in other ways.
While editing entries, if you receive an error message that states "Client error: Invalid text encoding: Cannot display non-Unicode posts unless default encoding has been selected", see http://www.livejournal.com/support/faqbrowse.bml?faqid=133. This process will need to be done by the community maintainer, while logged in as the community journal.
Note that while you can view entries posted by others when editing with a downloaded client or through http://www.livejournal.com/editjournal.bml, you can not edit or delete them unless you are the original author or have maintainer privileges.
USING THE WEB INTERFACE:
How you edit with the web interface depends on which style system you are using. To find out whether you are using S1 or S2, go to http://www.livejournal.com/customize/. The style system you are using will be displayed in the drop down box.
If you are using S1, go to the "Post Comments" or "Read Comments" page for the entry you want to edit or delete. You can get to these pages by clicking on the entry's comment links if comments are enabled, or by using the Calendar view (http://www.livejournal.com/support/faqbrowse.bml?faqid=70). On a small blue toolbar near the top of the page, if you're logged in, you should see an Edit Entry button (a blue pencil icon). Click it to go to the Edit Journal Entry page. There you can make the changes you want. Click "Save Journal Entry" to save your changes or "Delete Entry" to remove the entry entirely.
If you are using S2, you can edit entries at http://www.livejournal.com/editjournal.bml. This page allows you to choose an entry to edit either from the most recent entries or from a specific date. To retrieve a community's entries rather than your own, you will need to enter the community's username in the "In community" text box.
USING A DOWNLOADED CLIENT:
Many clients available for download include the ability to edit journal entries. For more information on your preferred client, consult its documentation or its menu options. See http://www.livejournal.com/support/faqbrowse.bml?faqid=158 for information on downloading a client.